This SBIR Phase I project will develop a novel branched copolymer as a peptide drug delivery carrier for pharmacological application. The carrier is a highly-structured copolymer that can form micelle-like structures with the peptide drug in aqueous media. The stability of this type of molecular structure will minimize early degradation of the encapsulated peptide drug and decrease harmful side-effects from premature drug release. The polymer/drug micelles will exhibit uniform size and drug loading level, and a predictable, well-controlled drug release rate. The overall objective in the Phase I program is to develop a drug delivery system based on the proposed copolymer for pharmacological applications, especially for delivery of peptide drugs. The specific technical aims are: 1. Synthesis and characterization of the polymer drug carrier. 2. Optimization of the polymer/drug encapsulation process and investigation of the drug release rate. A commercially significant model peptide drug will be used for the encapsulation study. The drug release rate from the polymer/drug formulation will be investigated. 3. Determination of the polymer biocompatibility. The potential cytotoxicity of the synthesized polymer will be investigated using in vitro cytotoxicity assays. Potential markets for protein and peptide drug delivery are highly significant. Many of these drugs have stability problems and undesirable side effects. With this proposed new drug delivery system, more efficient drug delivery with lower dosage is possible. This will reduce untoward side effects and enable efficient drug therapy for disease treatment. New drug delivery systems have had an impact on nearly every branch of medicine. Controlled drug delivery is a $20 billion industry and rising rapidly.